Conventional pasteurizing method uses plate heat exchangers, where the transmission of heat is carried out through a surface that is heated to a temperature far above the temperature required to obtain the proper heat treatment. Beside being energetically very inefficient, this method is causing many problems to the users, such as off-flavour, browning, cooked flavor and burnt deposits on the heating surfaces. Even though pasteurization is considered as the most efficient means to conical bacteria contamination, heat-resisting bacteria are not destroyed by the pasteurizing temperatures and processing times practical for this type of method. If sterilization is required for long-time conservation, one must add chemical preservatives.